/*
 * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
 * All rights reserved. 
 * 
 * Redistribution and use in source and binary forms, with or without modification, 
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission. 
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED 
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT 
 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT 
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING 
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY 
 * OF SUCH DAMAGE.
 *
 * This file is part of the lwIP TCP/IP stack.
 * 
 * Author: Adam Dunkels <adam@sics.se>
 *
 */
#ifndef __LWIP_TCP_H__
#define __LWIP_TCP_H__

#include "lwip/opt.h"

#if LWIP_TCP			/* don't build if not configured for use in lwipopts.h */

#include "lwip/sys.h"
#include "lwip/mem.h"
#include "lwip/pbuf.h"
#include "lwip/ip.h"
#include "lwip/icmp.h"
#include "lwip/err.h"

#ifdef __cplusplus
extern "C"
{
#endif

  struct tcp_pcb;

/* Functions for interfacing with TCP: */

/* Lower layer interface to TCP: */
#define tcp_init()		/* Compatibility define, not init needed. */
  void tcp_tmr (void);		/* Must be called every
				   TCP_TMR_INTERVAL
				   ms. (Typically 250 ms). */
/* Application program's interface: */
  struct tcp_pcb *tcp_new (void);
  struct tcp_pcb *tcp_alloc (u8_t prio);

  void tcp_arg (struct tcp_pcb *pcb, void *arg);
  void tcp_accept (struct tcp_pcb *pcb,
		   err_t (*accept) (void *arg, struct tcp_pcb * newpcb,
				    err_t err));
  void tcp_recv (struct tcp_pcb *pcb,
		 err_t (*recv) (void *arg, struct tcp_pcb * tpcb,
				struct pbuf * p, err_t err));
  void tcp_sent (struct tcp_pcb *pcb,
		 err_t (*sent) (void *arg, struct tcp_pcb * tpcb, u16_t len));
  void tcp_poll (struct tcp_pcb *pcb,
		 err_t (*poll) (void *arg, struct tcp_pcb * tpcb),
		 u8_t interval);
  void tcp_err (struct tcp_pcb *pcb, void (*err) (void *arg, err_t err));

#define          tcp_mss(pcb)      ((pcb)->mss)
#define          tcp_sndbuf(pcb)   ((pcb)->snd_buf)

#if TCP_LISTEN_BACKLOG
#define          tcp_accepted(pcb) (((struct tcp_pcb_listen *)(pcb))->accepts_pending--)
#else				/* TCP_LISTEN_BACKLOG */
#define          tcp_accepted(pcb)
#endif				/* TCP_LISTEN_BACKLOG */

  void tcp_recved (struct tcp_pcb *pcb, u16_t len);
  err_t tcp_bind (struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port);
  err_t tcp_connect (struct tcp_pcb *pcb, struct ip_addr *ipaddr,
		     u16_t port, err_t (*connected) (void *arg,
						     struct tcp_pcb * tpcb,
						     err_t err));

  struct tcp_pcb *tcp_listen_with_backlog (struct tcp_pcb *pcb, u8_t backlog);
#define          tcp_listen(pcb) tcp_listen_with_backlog(pcb, TCP_DEFAULT_LISTEN_BACKLOG)

  void tcp_abort (struct tcp_pcb *pcb);
  err_t tcp_close (struct tcp_pcb *pcb);

/* Flags for "apiflags" parameter in tcp_write and tcp_enqueue */
#define TCP_WRITE_FLAG_COPY 0x01
#define TCP_WRITE_FLAG_MORE 0x02

  err_t tcp_write (struct tcp_pcb *pcb, const void *dataptr, u16_t len,
		   u8_t apiflags);

  void tcp_setprio (struct tcp_pcb *pcb, u8_t prio);

#define TCP_PRIO_MIN    1
#define TCP_PRIO_NORMAL 64
#define TCP_PRIO_MAX    127

/* It is also possible to call these two functions at the right
   intervals (instead of calling tcp_tmr()). */
  void tcp_slowtmr (void);
  void tcp_fasttmr (void);


/* Only used by IP to pass a TCP segment to TCP: */
  void tcp_input (struct pbuf *p, struct netif *inp);
/* Used within the TCP code only: */
  err_t tcp_output (struct tcp_pcb *pcb);
  void tcp_rexmit (struct tcp_pcb *pcb);
  void tcp_rexmit_rto (struct tcp_pcb *pcb);

/**
 * This is the Nagle algorithm: inhibit the sending of new TCP
 * segments when new outgoing data arrives from the user if any
 * previously transmitted data on the connection remains
 * unacknowledged.
 */
#define tcp_do_output_nagle(tpcb) ((((tpcb)->unacked == NULL) || \
                            ((tpcb)->flags & TF_NODELAY) || \
                            (((tpcb)->unsent != NULL) && ((tpcb)->unsent->next != NULL))) ? \
                                1 : 0)
#define tcp_output_nagle(tpcb) (tcp_do_output_nagle(tpcb) ? tcp_output(tpcb) : ERR_OK)


/** This returns a TCP header option for MSS in an u32_t */
#define TCP_BUILD_MSS_OPTION()  htonl(((u32_t)2 << 24) | \
                                ((u32_t)4 << 16) | \
                                (((u32_t)TCP_MSS / 256) << 8) | \
                                (TCP_MSS & 255))

#define TCP_SEQ_LT(a,b)     ((s32_t)((a)-(b)) < 0)
#define TCP_SEQ_LEQ(a,b)    ((s32_t)((a)-(b)) <= 0)
#define TCP_SEQ_GT(a,b)     ((s32_t)((a)-(b)) > 0)
#define TCP_SEQ_GEQ(a,b)    ((s32_t)((a)-(b)) >= 0)
/* is b<=a<=c? */
#if 0				/* see bug #10548 */
#define TCP_SEQ_BETWEEN(a,b,c) ((c)-(b) >= (a)-(b))
#endif
#define TCP_SEQ_BETWEEN(a,b,c) (TCP_SEQ_GEQ(a,b) && TCP_SEQ_LEQ(a,c))
#define TCP_FIN 0x01U
#define TCP_SYN 0x02U
#define TCP_RST 0x04U
#define TCP_PSH 0x08U
#define TCP_ACK 0x10U
#define TCP_URG 0x20U
#define TCP_ECE 0x40U
#define TCP_CWR 0x80U

#define TCP_FLAGS 0x3fU

/* Length of the TCP header, excluding options. */
#define TCP_HLEN 20

#ifndef TCP_TMR_INTERVAL
#define TCP_TMR_INTERVAL       250	/* The TCP timer interval in milliseconds. */
#endif				/* TCP_TMR_INTERVAL */

#ifndef TCP_FAST_INTERVAL
#define TCP_FAST_INTERVAL      TCP_TMR_INTERVAL	/* the fine grained timeout in milliseconds */
#endif				/* TCP_FAST_INTERVAL */

#ifndef TCP_SLOW_INTERVAL
#define TCP_SLOW_INTERVAL      (2*TCP_TMR_INTERVAL)	/* the coarse grained timeout in milliseconds */
#endif				/* TCP_SLOW_INTERVAL */

#define TCP_FIN_WAIT_TIMEOUT 20000	/* milliseconds */
#define TCP_SYN_RCVD_TIMEOUT 20000	/* milliseconds */

#define TCP_OOSEQ_TIMEOUT        6U	/* x RTO */

#ifndef TCP_MSL
#define TCP_MSL 60000U		/* The maximum segment lifetime in milliseconds */
#endif

/* Keepalive values, compliant with RFC 1122. Don't change this unless you know what you're doing */
#ifndef  TCP_KEEPIDLE_DEFAULT
#define  TCP_KEEPIDLE_DEFAULT     7200000UL	/* Default KEEPALIVE timer in milliseconds */
#endif

#ifndef  TCP_KEEPINTVL_DEFAULT
#define  TCP_KEEPINTVL_DEFAULT    75000UL	/* Default Time between KEEPALIVE probes in milliseconds */
#endif

#ifndef  TCP_KEEPCNT_DEFAULT
#define  TCP_KEEPCNT_DEFAULT      9U	/* Default Counter for KEEPALIVE probes */
#endif

#define  TCP_MAXIDLE              TCP_KEEPCNT_DEFAULT * TCP_KEEPINTVL_DEFAULT	/* Maximum KEEPALIVE probe time */

/* Fields are (of course) in network byte order.
 * Some fields are converted to host byte order in tcp_input().
 */
#ifdef PACK_STRUCT_USE_INCLUDES
#  include "arch/bpstruct.h"
#endif
  PACK_STRUCT_BEGIN struct tcp_hdr
  {
    PACK_STRUCT_FIELD (u16_t src);
    PACK_STRUCT_FIELD (u16_t dest);
    PACK_STRUCT_FIELD (u32_t seqno);
    PACK_STRUCT_FIELD (u32_t ackno);
    PACK_STRUCT_FIELD (u16_t _hdrlen_rsvd_flags);
    PACK_STRUCT_FIELD (u16_t wnd);
    PACK_STRUCT_FIELD (u16_t chksum);
    PACK_STRUCT_FIELD (u16_t urgp);
  } PACK_STRUCT_STRUCT;
    PACK_STRUCT_END
#ifdef PACK_STRUCT_USE_INCLUDES
#  include "arch/epstruct.h"
#endif
#define TCPH_OFFSET(phdr) (ntohs((phdr)->_hdrlen_rsvd_flags) >> 8)
#define TCPH_HDRLEN(phdr) (ntohs((phdr)->_hdrlen_rsvd_flags) >> 12)
#define TCPH_FLAGS(phdr)  (ntohs((phdr)->_hdrlen_rsvd_flags) & TCP_FLAGS)
#define TCPH_OFFSET_SET(phdr, offset) (phdr)->_hdrlen_rsvd_flags = htons(((offset) << 8) | TCPH_FLAGS(phdr))
#define TCPH_HDRLEN_SET(phdr, len) (phdr)->_hdrlen_rsvd_flags = htons(((len) << 12) | TCPH_FLAGS(phdr))
#define TCPH_FLAGS_SET(phdr, flags) (phdr)->_hdrlen_rsvd_flags = htons((ntohs((phdr)->_hdrlen_rsvd_flags) & ~TCP_FLAGS) | (flags))
#define TCPH_SET_FLAG(phdr, flags ) (phdr)->_hdrlen_rsvd_flags = htons(ntohs((phdr)->_hdrlen_rsvd_flags) | (flags))
#define TCPH_UNSET_FLAG(phdr, flags) (phdr)->_hdrlen_rsvd_flags = htons(ntohs((phdr)->_hdrlen_rsvd_flags) | (TCPH_FLAGS(phdr) & ~(flags)) )
#define TCP_TCPLEN(seg) ((seg)->len + ((TCPH_FLAGS((seg)->tcphdr) & TCP_FIN || \
          TCPH_FLAGS((seg)->tcphdr) & TCP_SYN)? 1: 0))
    enum tcp_state
  {
    CLOSED = 0,
    LISTEN = 1,
    SYN_SENT = 2,
    SYN_RCVD = 3,
    ESTABLISHED = 4,
    FIN_WAIT_1 = 5,
    FIN_WAIT_2 = 6,
    CLOSE_WAIT = 7,
    CLOSING = 8,
    LAST_ACK = 9,
    TIME_WAIT = 10
  };

/** Flags used on input processing, not on pcb->flags
*/
#define TF_RESET     (u8_t)0x08U	/* Connection was reset. */
#define TF_CLOSED    (u8_t)0x10U	/* Connection was sucessfully closed. */
#define TF_GOT_FIN   (u8_t)0x20U	/* Connection was closed by the remote end. */

/**
 * members common to struct tcp_pcb and struct tcp_listen_pcb
 */
#define TCP_PCB_COMMON(type) \
  type *next; /* for the linked list */ \
  enum tcp_state state; /* TCP state */ \
  u8_t prio; \
  void *callback_arg; \
  /* ports are in host byte order */ \
  u16_t local_port

/* the TCP protocol control block */
  struct tcp_pcb
  {
/** common PCB members */
    IP_PCB;
/** protocol specific PCB members */
    TCP_PCB_COMMON (struct tcp_pcb);

    /* ports are in host byte order */
    u16_t remote_port;

    u8_t flags;
#define TF_ACK_DELAY   (u8_t)0x01U	/* Delayed ACK. */
#define TF_ACK_NOW     (u8_t)0x02U	/* Immediate ACK. */
#define TF_INFR        (u8_t)0x04U	/* In fast recovery. */
#define TF_FIN         (u8_t)0x20U	/* Connection was closed locally (FIN segment enqueued). */
#define TF_NODELAY     (u8_t)0x40U	/* Disable Nagle algorithm */
#define TF_NAGLEMEMERR (u8_t)0x80U	/* nagle enabled, memerr, try to output to prevent delayed ACK to happen */

    /* the rest of the fields are in host byte order
       as we have to do some math with them */
    /* receiver variables */
    u32_t rcv_nxt;		/* next seqno expected */
    u16_t rcv_wnd;		/* receiver window */
    u16_t rcv_ann_wnd;		/* announced receive window */

    /* Timers */
    u32_t tmr;
    u8_t polltmr, pollinterval;

    /* Retransmission timer. */
    s16_t rtime;

    u16_t mss;			/* maximum segment size */

    /* RTT (round trip time) estimation variables */
    u32_t rttest;		/* RTT estimate in 500ms ticks */
    u32_t rtseq;		/* sequence number being timed */
    s16_t sa, sv;		/* @todo document this */

    s16_t rto;			/* retransmission time-out */
    u8_t nrtx;			/* number of retransmissions */

    /* fast retransmit/recovery */
    u32_t lastack;		/* Highest acknowledged seqno. */
    u8_t dupacks;

    /* congestion avoidance/control variables */
    u16_t cwnd;
    u16_t ssthresh;

    /* sender variables */
    u32_t snd_nxt,		/* next seqno to be sent */
      snd_max;			/* Highest seqno sent. */
    u16_t snd_wnd;		/* sender window */
    u32_t snd_wl1, snd_wl2,	/* Sequence and acknowledgement numbers of last
				   window update. */
      snd_lbb;			/* Sequence number of next byte to be buffered. */

    u16_t acked;

    u16_t snd_buf;		/* Available buffer space for sending (in bytes). */
#define TCP_SNDQUEUELEN_OVERFLOW (0xffff-3)
    u16_t snd_queuelen;		/* Available buffer space for sending (in tcp_segs). */


    /* These are ordered by sequence number: */
    struct tcp_seg *unsent;	/* Unsent (queued) segments. */
    struct tcp_seg *unacked;	/* Sent but unacknowledged segments. */
#if TCP_QUEUE_OOSEQ
    struct tcp_seg *ooseq;	/* Received out of sequence segments. */
#endif				/* TCP_QUEUE_OOSEQ */

    struct pbuf *refused_data;	/* Data previously received but not yet taken by upper layer */

#if LWIP_CALLBACK_API
    /* Function to be called when more send buffer space is available.
     * @param arg user-supplied argument (tcp_pcb.callback_arg)
     * @param pcb the tcp_pcb which has send buffer space available
     * @param space the amount of bytes available
     * @return ERR_OK: try to send some data by calling tcp_output
     */
      err_t (*sent) (void *arg, struct tcp_pcb * pcb, u16_t space);

    /* Function to be called when (in-sequence) data has arrived.
     * @param arg user-supplied argument (tcp_pcb.callback_arg)
     * @param pcb the tcp_pcb for which data has arrived
     * @param p the packet buffer which arrived
     * @param err an error argument (TODO: that is current always ERR_OK?)
     * @return ERR_OK: try to send some data by calling tcp_output
     */
      err_t (*recv) (void *arg, struct tcp_pcb * pcb, struct pbuf * p,
		     err_t err);

    /* Function to be called when a connection has been set up.
     * @param arg user-supplied argument (tcp_pcb.callback_arg)
     * @param pcb the tcp_pcb that now is connected
     * @param err an error argument (TODO: that is current always ERR_OK?)
     * @return value is currently ignored
     */
      err_t (*connected) (void *arg, struct tcp_pcb * pcb, err_t err);

    /* Function to call when a listener has been connected.
     * @param arg user-supplied argument (tcp_pcb.callback_arg)
     * @param pcb a new tcp_pcb that now is connected
     * @param err an error argument (TODO: that is current always ERR_OK?)
     * @return ERR_OK: accept the new connection,
     *                 any other err_t abortsthe new connection
     */
      err_t (*accept) (void *arg, struct tcp_pcb * newpcb, err_t err);

    /* Function which is called periodically.
     * The period can be adjusted in multiples of the TCP slow timer interval
     * by changing tcp_pcb.polltmr.
     * @param arg user-supplied argument (tcp_pcb.callback_arg)
     * @param pcb the tcp_pcb to poll for
     * @return ERR_OK: try to send some data by calling tcp_output
     */
      err_t (*poll) (void *arg, struct tcp_pcb * pcb);

    /* Function to be called whenever a fatal error occurs.
     * There is no pcb parameter since most of the times, the pcb is
     * already deallocated (or there is no pcb) when this function is called.
     * @param arg user-supplied argument (tcp_pcb.callback_arg)
     * @param err an indication why the error callback is called:
     *            ERR_ABRT: aborted through tcp_abort or by a TCP timer
     *            ERR_RST: the connection was reset by the remote host
     */
    void (*errf) (void *arg, err_t err);
#endif				/* LWIP_CALLBACK_API */

    /* idle time before KEEPALIVE is sent */
    u32_t keep_idle;
#if LWIP_TCP_KEEPALIVE
    u32_t keep_intvl;
    u32_t keep_cnt;
#endif				/* LWIP_TCP_KEEPALIVE */

    /* Persist timer counter */
    u32_t persist_cnt;
    /* Persist timer back-off */
    u8_t persist_backoff;

    /* KEEPALIVE counter */
    u8_t keep_cnt_sent;
  };

  struct tcp_pcb_listen
  {
/* Common members of all PCB types */
    IP_PCB;
/* Protocol specific PCB members */
    TCP_PCB_COMMON (struct tcp_pcb_listen);

#if LWIP_CALLBACK_API
    /* Function to call when a listener has been connected.
     * @param arg user-supplied argument (tcp_pcb.callback_arg)
     * @param pcb a new tcp_pcb that now is connected
     * @param err an error argument (TODO: that is current always ERR_OK?)
     * @return ERR_OK: accept the new connection,
     *                 any other err_t abortsthe new connection
     */
      err_t (*accept) (void *arg, struct tcp_pcb * newpcb, err_t err);
#endif				/* LWIP_CALLBACK_API */
#if TCP_LISTEN_BACKLOG
    u8_t backlog;
    u8_t accepts_pending;
#endif				/* TCP_LISTEN_BACKLOG */
  };

#if LWIP_EVENT_API

  enum lwip_event
  {
    LWIP_EVENT_ACCEPT,
    LWIP_EVENT_SENT,
    LWIP_EVENT_RECV,
    LWIP_EVENT_CONNECTED,
    LWIP_EVENT_POLL,
    LWIP_EVENT_ERR
  };

  err_t lwip_tcp_event (void *arg, struct tcp_pcb *pcb,
			enum lwip_event,
			struct pbuf *p, u16_t size, err_t err);

#define TCP_EVENT_ACCEPT(pcb,err,ret)    ret = lwip_tcp_event((pcb)->callback_arg, (pcb),\
                LWIP_EVENT_ACCEPT, NULL, 0, err)
#define TCP_EVENT_SENT(pcb,space,ret) ret = lwip_tcp_event((pcb)->callback_arg, (pcb),\
                   LWIP_EVENT_SENT, NULL, space, ERR_OK)
#define TCP_EVENT_RECV(pcb,p,err,ret) ret = lwip_tcp_event((pcb)->callback_arg, (pcb),\
                LWIP_EVENT_RECV, (p), 0, (err))
#define TCP_EVENT_CONNECTED(pcb,err,ret) ret = lwip_tcp_event((pcb)->callback_arg, (pcb),\
                LWIP_EVENT_CONNECTED, NULL, 0, (err))
#define TCP_EVENT_POLL(pcb,ret)       ret = lwip_tcp_event((pcb)->callback_arg, (pcb),\
                LWIP_EVENT_POLL, NULL, 0, ERR_OK)
#define TCP_EVENT_ERR(errf,arg,err)  lwip_tcp_event((arg), NULL, \
                LWIP_EVENT_ERR, NULL, 0, (err))
#else				/* LWIP_EVENT_API */
#define TCP_EVENT_ACCEPT(pcb,err,ret)     \
                        if((pcb)->accept != NULL) \
                        (ret = (pcb)->accept((pcb)->callback_arg,(pcb),(err)))
#define TCP_EVENT_SENT(pcb,space,ret) \
                        if((pcb)->sent != NULL) \
                        (ret = (pcb)->sent((pcb)->callback_arg,(pcb),(space)))
#define TCP_EVENT_RECV(pcb,p,err,ret) \
                        if((pcb)->recv != NULL) \
                        { ret = (pcb)->recv((pcb)->callback_arg,(pcb),(p),(err)); } else { \
                          ret = ERR_OK; \
                          if (p) pbuf_free(p); }
#define TCP_EVENT_CONNECTED(pcb,err,ret) \
                        if((pcb)->connected != NULL) \
                        (ret = (pcb)->connected((pcb)->callback_arg,(pcb),(err)))
#define TCP_EVENT_POLL(pcb,ret) \
                        if((pcb)->poll != NULL) \
                        (ret = (pcb)->poll((pcb)->callback_arg,(pcb)))
#define TCP_EVENT_ERR(errf,arg,err) \
                        if((errf) != NULL) \
                        (errf)((arg),(err))
#endif				/* LWIP_EVENT_API */

/* This structure represents a TCP segment on the unsent and unacked queues */
  struct tcp_seg
  {
    struct tcp_seg *next;	/* used when putting segements on a queue */
    struct pbuf *p;		/* buffer containing data + TCP header */
    void *dataptr;		/* pointer to the TCP data in the pbuf */
    u16_t len;			/* the TCP length of this segment */
    struct tcp_hdr *tcphdr;	/* the TCP header */
  };

/* Internal functions and global variables: */
  struct tcp_pcb *tcp_pcb_copy (struct tcp_pcb *pcb);
  void tcp_pcb_purge (struct tcp_pcb *pcb);
  void tcp_pcb_remove (struct tcp_pcb **pcblist, struct tcp_pcb *pcb);

  u8_t tcp_segs_free (struct tcp_seg *seg);
  u8_t tcp_seg_free (struct tcp_seg *seg);
  struct tcp_seg *tcp_seg_copy (struct tcp_seg *seg);

#define tcp_ack(pcb)     if((pcb)->flags & TF_ACK_DELAY) { \
                            (pcb)->flags &= ~TF_ACK_DELAY; \
                            (pcb)->flags |= TF_ACK_NOW; \
                            tcp_output(pcb); \
                         } else { \
                            (pcb)->flags |= TF_ACK_DELAY; \
                         }

#define tcp_ack_now(pcb) (pcb)->flags |= TF_ACK_NOW; \
                         tcp_output(pcb)

  err_t tcp_send_ctrl (struct tcp_pcb *pcb, u8_t flags);
  err_t tcp_enqueue (struct tcp_pcb *pcb, void *dataptr, u16_t len,
		     u8_t flags, u8_t apiflags, u8_t * optdata, u8_t optlen);

  void tcp_rexmit_seg (struct tcp_pcb *pcb, struct tcp_seg *seg);

  void tcp_rst (u32_t seqno, u32_t ackno,
		struct ip_addr *local_ip, struct ip_addr *remote_ip,
		u16_t local_port, u16_t remote_port);

  u32_t tcp_next_iss (void);

  void tcp_keepalive (struct tcp_pcb *pcb);
  void tcp_zero_window_probe (struct tcp_pcb *pcb);

#if TCP_CALCULATE_EFF_SEND_MSS
  u16_t tcp_eff_send_mss (u16_t sendmss, struct ip_addr *addr);
#endif				/* TCP_CALCULATE_EFF_SEND_MSS */

  extern struct tcp_pcb *tcp_input_pcb;
  extern u32_t tcp_ticks;

#if TCP_DEBUG || TCP_INPUT_DEBUG || TCP_OUTPUT_DEBUG
  void tcp_debug_print (struct tcp_hdr *tcphdr);
  void tcp_debug_print_flags (u8_t flags);
  void tcp_debug_print_state (enum tcp_state s);
  void tcp_debug_print_pcbs (void);
  s16_t tcp_pcbs_sane (void);
#else
#  define tcp_debug_print(tcphdr)
#  define tcp_debug_print_flags(flags)
#  define tcp_debug_print_state(s)
#  define tcp_debug_print_pcbs()
#  define tcp_pcbs_sane() 1
#endif				/* TCP_DEBUG */

#if NO_SYS
#define tcp_timer_needed()
#else
  void tcp_timer_needed (void);
#endif

/* The TCP PCB lists. */
  union tcp_listen_pcbs_t
  {				/* List of all TCP PCBs in LISTEN state. */
    struct tcp_pcb_listen *listen_pcbs;
    struct tcp_pcb *pcbs;
  };
  extern union tcp_listen_pcbs_t tcp_listen_pcbs;
  extern struct tcp_pcb *tcp_active_pcbs;	/* List of all TCP PCBs that are in a
						   state in which they accept or send
						   data. */
  extern struct tcp_pcb *tcp_tw_pcbs;	/* List of all TCP PCBs in TIME-WAIT. */

  extern struct tcp_pcb *tcp_tmp_pcb;	/* Only used for temporary storage. */

/* Axioms about the above lists:   
   1) Every TCP PCB that is not CLOSED is in one of the lists.
   2) A PCB is only in one of the lists.
   3) All PCBs in the tcp_listen_pcbs list is in LISTEN state.
   4) All PCBs in the tcp_tw_pcbs list is in TIME-WAIT state.
*/

/* Define two macros, TCP_REG and TCP_RMV that registers a TCP PCB
   with a PCB list or removes a PCB from a list, respectively. */
#if 0
#define TCP_REG(pcbs, npcb) do {\
                            LWIP_DEBUGF(TCP_DEBUG, ("TCP_REG %p local port %d\n", npcb, npcb->local_port)); \
                            for(tcp_tmp_pcb = *pcbs; \
          tcp_tmp_pcb != NULL; \
        tcp_tmp_pcb = tcp_tmp_pcb->next) { \
                                LWIP_ASSERT("TCP_REG: already registered\n", tcp_tmp_pcb != npcb); \
                            } \
                            LWIP_ASSERT("TCP_REG: pcb->state != CLOSED", npcb->state != CLOSED); \
                            npcb->next = *pcbs; \
                            LWIP_ASSERT("TCP_REG: npcb->next != npcb", npcb->next != npcb); \
                            *(pcbs) = npcb; \
                            LWIP_ASSERT("TCP_RMV: tcp_pcbs sane", tcp_pcbs_sane()); \
              tcp_timer_needed(); \
                            } while(0)
#define TCP_RMV(pcbs, npcb) do { \
                            LWIP_ASSERT("TCP_RMV: pcbs != NULL", *pcbs != NULL); \
                            LWIP_DEBUGF(TCP_DEBUG, ("TCP_RMV: removing %p from %p\n", npcb, *pcbs)); \
                            if(*pcbs == npcb) { \
                               *pcbs = (*pcbs)->next; \
                            } else for(tcp_tmp_pcb = *pcbs; tcp_tmp_pcb != NULL; tcp_tmp_pcb = tcp_tmp_pcb->next) { \
                               if(tcp_tmp_pcb->next != NULL && tcp_tmp_pcb->next == npcb) { \
                                  tcp_tmp_pcb->next = npcb->next; \
                                  break; \
                               } \
                            } \
                            npcb->next = NULL; \
                            LWIP_ASSERT("TCP_RMV: tcp_pcbs sane", tcp_pcbs_sane()); \
                            LWIP_DEBUGF(TCP_DEBUG, ("TCP_RMV: removed %p from %p\n", npcb, *pcbs)); \
                            } while(0)

#else				/* LWIP_DEBUG */
#define TCP_REG(pcbs, npcb) do { \
                            npcb->next = *pcbs; \
                            *(pcbs) = npcb; \
              tcp_timer_needed(); \
                            } while(0)
#define TCP_RMV(pcbs, npcb) do { \
                            if(*(pcbs) == npcb) { \
                               (*(pcbs)) = (*pcbs)->next; \
                            } else for(tcp_tmp_pcb = *pcbs; tcp_tmp_pcb != NULL; tcp_tmp_pcb = tcp_tmp_pcb->next) { \
                               if(tcp_tmp_pcb->next != NULL && tcp_tmp_pcb->next == npcb) { \
                                  tcp_tmp_pcb->next = npcb->next; \
                                  break; \
                               } \
                            } \
                            npcb->next = NULL; \
                            } while(0)
#endif				/* LWIP_DEBUG */

#ifdef __cplusplus
}
#endif

#endif				/* LWIP_TCP */

#endif				/* __LWIP_TCP_H__ */
